1. Field of Invention
The present invention relates in general to a light source module, and more particularly, to a backlight unit for a liquid crystal display.
2. Related Art
In modern multimedia technology, the conventional analog transmission of image information has been replaced by digital transmission. To comply with the modern life style, the multimedia applications such as video or image devices have been made very thin and light. The conventional cathode ray display, though having the advantages of fine display quality and low cost, can no longer meet with the market requirements due to the large volume and heavy weight required by the internal cathode cavity. Further, the cathode ray tube display also has the problem of high radiation that often deteriorates functions of human eyes. Therefore, recently the mature optoelectronic and semiconductor made it possible to have the flat panel displays dominating the display market. Among various types of flat panel display, the liquid crystal display characterized with low operation voltage, non-radiation scattering, light weight and small volume has become the mainstream of display product.
A typical liquid crystal display includes a liquid crystal display panel and a backlight unit. The liquid crystal display panel includes a color filter (C/F), a thin-film transistor array, and a liquid crystal layer sandwiched between two substrates. The backlight unit is operative to provide the source light required by the liquid crystal panel, so as to achieve the display effect. The thin-film transistor array formed on the substrate determines the number of pixels of the liquid crystal display. The electrode pair of each pixel provides voltage to drive the liquid crystal molecules twisting between them, so as to drive whether a light beam can propagate through or not. In addition, a specific response time is required for twisting the liquid crystal molecules to a desired orientation. Therefore, double image often appears during the time the liquid crystal molecules are driven to twist to the desired orientation. Such longer motion picture response is always an adverse effect that degrades the display quality of the liquid crystal display.
To resolve the double-image problem, a scan backlight unit has been proposed. FIG. 1 shows a schematic drawing of a conventional scan backlight unit. As shown, the scan backlight unit 104 includes a frame 110, multiple sets of light source 120, a diffuser 140 and at least one optical film 142. The light source sets 120 are located on the bottom surface of the frame 110. Each of the light source sets 120 includes three periodically driven individual light sources. The light required by the liquid crystal panel is supplied from these light source sets 120, and each light source set 120 corresponds to a specific area of the liquid crystal panel 102. The diffuser 140 is operative to evenly diffuse light emitted from the light sources 122, and the optical film 142 is used to enhance the optical quality of the backlight unit 104.
Although the generation of double images can be suppressed by periodically driving the light source sets of the scan backlight unit 104, the response time between lit up the light source set 120 and the liquid crystal molecules being twisted still exists. In addition, even when the liquid crystal molecules are sufficiently twisted, interference between different light source sets may occur. That is, the light emitted from any of the light source sets 120 may propagate to any area corresponding to other light source set to cause double image.
It is therefore a substantially need to suppress generation of double image caused by the backlight unit.